1. Field of the Invention
The present invention relates to a mower unit attached to a lawn tractor or the like and having a bevel gear mechanism.
2. Description of the Related Art
This type of mower unit is disclosed in Japanese Utility Model Publication No. 1993-15722 and U.S. Pat. No. 5,064,315, for example. This mower unit includes an input shaft extending substantially horizontally, a first bevel gear mounted on the input shaft, an output shaft extending substantially vertically, a second bevel gear meshed with the first bevel gear and mounted on one end of the output shaft, a blade mounted on the other end of the output shaft, a blade housing covering the blade, a beating holder rotatably supporting the output shaft, a bevel gear case enclosing the first and second bevel gears, and a pair of right and left support stays connected to the bevel gear case to mount the bevel gear case to the blade housing.
The mower unit is formed into an integral whole with the bearing holder, bevel gear case and blade housing connected to one another by bolts. Where the bearing holder and bevel gear case, i.e. the bearing holder and support stays, are not interconnected in exact alignment, the positional precision between the bevel gear case and beating holder, and hence the angle between the output shaft and input shaft, deviates from a desired value. This deviation, even if small, will produce increased noise due to meshing between the first and second bevel gears. The blade housing, since it is formed of a plate material, inevitably has an uneven plate thickness and a deformation occurring in time of manufacture. Consequently, where the bevel gear case and support stays are interconnected particularly with the blade housing interposed therebetween, the positional precision between the bevel gear case and bearing holder fails to attain a required level.